TATA PUNCH-SERVICE MANUAL

SUPPLEMENTARY RESTRAINT SYSTEM (SRS) 21 Front Seat (Driver) Belt buckle Front Seat (Co-Driver) Belt buckle 4. RETRACTOR PRE-TENSIONER DIGRESSIVE LOAD LIMITER (RPDLL) AND ANCHOR PRE TENSIONER (APT) - (DRIVER SIDE) Seatbelt pre-tensioner is a device installed in vehicles to reduce slack that may exist in a seatbelt system at the moment of a frontal collision. Having the seatbelt system snug allows the supplemental restraint airbag system to work most effectively. A loose seatbelt system does not keep the occupant in the proper position during the forces of a crash. In order for airbags to reduce or eliminate injury, the occupant must be seated, belted and in the correct position in the vehicle. Pretensioner device is mounted in the retractor unit. The Pretensioner unit essentially consists of a ball cage comprising of a tube of steel balls surrounding a toothed wheel. The wheel is mounted on the belt-webbing spool. When the ECU senses a crash, depending on the crash severity, it sends a "fire" signal to the squib in the belt Pretensioner. The firing of the squib causes displacement of the balls in the tube. The movement of the balls causes rotation of the toothed wheel, which in turn rotates the webbing spool and removes the slack from the belt. The purpose of the APT is to remove the belt slack in case of an crash incident. That allows an optimized coupling of the occupant to the seat, thus earlier deceleration and mitigation of the submarining effect occurs.